Re: [TowerTalk] Re: 20M Yagi Interaction with nearby objects

[Jim Lux <jimlux@earthlink.net>]

At 03:23 PM 10/20/2003 -0400, Pete Smith wrote:
> A
> > > I have tried to model the situation with NEC2 but had no succes in making
> > > a workable model (too many segments)
>
> I think your concerns are fully justified, Con.  After all, 
> electromagnetic radiation obeys the inverse square law, so the current in 
> the roof will become greater the closer the antenna is to it.

Worse than that... it's only inverse square in the far field, where the 
source can be reasonably approximated as a point source.  In the near field 
[which you certainly are in (rule of thumb is 2 pi wavelengths for antennae 
that are <1 wavelength in size)], this assumption isn't valid.  For 
instance the magnetic field around a linear conductor only drops off as 1/r.

Jim, W6RMK



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